The invention relates to a medical instrument with a shaft which is connected at the proximal end to a handle, with an insert which can be guided along the shaft and which is connected at the proximal end to a movable grip part of the handle and at its distal end has a tool which can be actuated by pivoting of the grip part, and with a lock which can be brought into locking engagement with the movable grip part.
A medical instrument of this kind in the form of dissecting forceps or gripping forceps is known from page 77 of section 4 “Dissecting forceps and gripping forceps” of the catalogue of the firm Karl Storz GmbH & Co. KG, Tuttlingen, Germany “Laparoskopie”, 5th edition January 2005.
The movable grip part, which actuates the tool, can be fixed by means of the lock. The lock is in most cases composed of a rod-shaped grip part, which is mounted on a handle, in most cases at an immovable grip part. On the side directed towards the movable grip part, the lock has teeth that engage with a locking pin on the movable grip part.
In some designs, the inclination of the flank of the teeth is such that the movable grip part can run over the teeth in one direction, while a movement in the opposite direction is blocked.
A common practical use is that of gripping forceps in which, after a section of tissue has been gripped, the movable grip part is locked by means of the lock, such that the jaw parts are held in a defined position. In some designs however, as has already been mentioned, it is possible to move the movable grip part in one direction, mostly into the closing position of the jaw parts, such that the secured tissue is held still more firmly than before. However, a movement in the opposite direction, i.e. further opening of the jaw parts, is blocked by the lock. This ensures that a tissue that has been gripped is no longer released, such that the operator is able to concentrate on other procedures that he might wish to perform with the forceps, for example coagulation or the like.
Should the operator wish to release the lock, he has to move the latter away from the grip part, and only then is he able to move the movable grip part in both directions again. However, since the lever-type lock is often pretensioned by a spring force, the operator has to hold the lock permanently away if he wishes to move the second grip part freely back and forth.
This is ergonomically disadvantageous and occupies at least one finger of the hand, which finger has to press the lock permanently away.
In medical instruments with a bendable shaft, a further control element is provided on the instrument, namely the control element via which the shaft is bent.
In some designs, particularly in dissecting forceps, it is desirable for the movable grip part to be fixed via a lock in some manoeuvres, while in other manoeuvres, for example cutting, it is desirable for it to be movable freely in both directions. Since, in the case of an instrument with a bendable shaft, dissecting work is also intended to be performed with the shaft bent, the operator has to be able to manoeuvre several adjusting elements and be able to control their locking or release.
Since medical instruments of this kind are mostly used in minimally invasive surgery, the field of view of the operator at the distal end is in any case limited and he has to view this area either through an endoscope or on a monitor arranged alongside, and it is therefore very important that he is able to achieve the various control states using the fingers of the hand with which he has taken hold of the medical instrument, and that he is able to do so in a manner that is as ergonomic as possible.
It is therefore object of the present invention to develop a medical instrument, particularly one with a bendable shaft, in such a way that more operationally reliable and ergonomic handling is possible, in particular as regards the locking and unlocking of the movable grip part.